Immobilization of Bacillus subtilis enzymes living on the surface of cotton

III.6. Effect of bead size on rate of starch hydrolysis

In the system of enzyme immobilization by entrapment, substrate has to be transported from the bulk solution to the outer surface of the matrix and then to the inner part of matrix. So both the intraparticular diffusion and the external mass transfer should be taken into consideration. However it is assumed that greater contribution is from the intraparticle mass transfer. The intraparticle mass transfer depends on size of the bead which has significant effect on the rate of starch hydrolysis [19]. As shown in Fig. 14, the highest rate of starch hydrolysis was observed with bead size of 2.4mm and the bigger sizes showed lower rate. From the above finding it may be concluded that the beads of 2.4 mm offered lesser diffusion resistance compared to the larger beads.